Standard equipment: open-end and box spanners

Open-end wrenches are the original form of wrench for bolts with polygonal heads (square, hexagonal, octagonal). With its two parallel jaws, the open-end wrench grips the screw head from the side. This is especially practical when head-on access to the screw head or nut is restricted. A problem is that the jaws can widen if the applied load is too high. The open-end wrench then only grips the edges of the polygon and will eventually round off the bolt head or nut. Since all bolts on old and older Harleys up until well into the 1980s — and even on later air-cooled Harleys still most bolts — have inch dimensions, you need open-end wrenches with SAE jaw sizes for wrenching on JD, Flat, Knuckle and Panhead, Shovel or Evo and Sportster. Such wrenches are available in sets or individually, e.g. from Bahco. Adjustable wrenches are available for on the go and as a one-size-fits-all tool when space in the tool roll is scarce. Incidentally, Bahco started out as B.A.Hjort & Co around 1892 with, among other things, the marketing of just such adjustable wrenches. These had also been patented in Sweden a year earlier by a Mr. Johansson.

Angled open-end jaw

All standard open-end wrenches have angled jaws. The most common angle is 15°. Have you ever thought about why this is the case? Without this angle at the base of the jaw, you would have to turn a screw with a hexagon head by at least 60° to be able to re-apply the jaw. With a 15° angled jaw, you can only turn the screw head by 30°, then swap the other side of the wrench upwards and reapply to turn another 30°. And then you start all over again. A clever trick when space and the available swivel angle are limited.

Wrench with bend and offset: the box spanner

To prevent a wrench jaw from bending open under heavy loads, simply close it. And —eureca! — voilà a box (or ring) wrench. A box wrench has a single or double hexagon punched into the ring for better power transmission. For better accessibility, the ring is angled (common with combination wrenches with ring and jaw) or offset. (Double ring wrenches are usually equipped in this way.) For hard-to-reach spaces on cylinder flanges and heads, there is also a ring wrench that is angled to the sides.